Ink set, ink jet recording apparatus, ink jet recording method, recording unit, and ink cartridge

ABSTRACT

The present invention provides an ink set, an ink jet recording apparatus, an ink jet recording method, a recording unit, and an ink cartridge, which can produce ink jet color images in which the color balance does not easily become unstable even if the image is stored for a long time, and in which the color images have greater durability so that degradation of the visual appearance is not easily recognizable even if the image is stored for a long time. The ink set includes a first aqueous ink and a second aqueous ink having the same color tone, the second ink having a lower coloring material content than that of the first ink, and the degree of fading of an image produced with the second ink is the same as or lower than that of an image produced with the first ink.

This is a divisional application of application Ser. No. 09/871,627,filed Jun. 4, 2001 now U.S. Pat. No. 6,706,100.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to ink sets, and more particularly,relates to an ink set that is suitable for use in ink jet recording inwhich an ink is ejected from an orifice in response to a recordingsignal in order to perform recording on a recording medium, as well asto an ink jet recording apparatus, an ink jet recording method, arecording unit, and an ink cartridge.

2. Description of the Related Art

Conventionally, aqueous inks in which dyes having various color tonesare dissolved in water-soluble media are used for color recording usingan ink jet recording method. It is desirable that the inks exhibit thefollowing ink jet recording characteristics (1) to (10) at as high adegree as possible.

-   -   (1) Produces images with adequate density;    -   (2) Satisfactorily dries on a recording medium;    -   (3) Smearing of the recorded image does not occur;    -   (4) Running of the recorded image does not occur when in contact        with water, alcohols, etc.;    -   (5) A recorded image with superior light-fastness is produced;    -   (6) Does not cause clogging at nozzles;    -   (7) Blurring of recorded images does not occur during continuous        printing or when recording is started after a long interval;    -   (8) Stable when stored;    -   (9) Problems do not occur even if inks are brought into contact        with components of the recording apparatus; and    -   (10) Has superior heat resistance and does not affect thermal        energy generation elements.

Furthermore, as demand for color ink jet recording increases, images ofhigher resolution and higher quality are being required. For thesepurposes, color images in the broad color reproduction range areachieved by selecting coloring materials having superior colordeveloping ability, and the dot size of images is decreased by producingsmall ink droplets, thereby achieving images with high resolution.Furthermore, by using two or more types of inks which have differentcoloring material contents but the same color tone, the inks can beselected depending on the density of the image, i.e., light colorportions and deep color portions, and by controlling variousink-applying processes, it is possible to produce smoother images. Usingthe techniques described above, ink jet recording methods have recentlybeen producing ink jet images of high quality, which are comparable tosilver halide photographs.

However, even if ink jet images of a quality comparable to silver halidephotographs are produced using the techniques described above, the colorbalance may become unstable depending on the environment in which theimages are stored and the visual appearance of the image may degrade,resulting in a loss in durability of the images. Therefore, there is anincreased demand for an ink jet image which has, in addition to highresolution, even more superior durability, for example, and which doesnot fade substantially even if stored for a long period of time.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an ink set which can producea color image that is able to maintain good color balance for a longperiod of time in which the color balance does not easily becomeunstable even if stored for a long time.

The present invention also provides an ink jet recording method and anink jet recording apparatus used therefor, which can produce colorimages having greater durability, i.e., degradation of the visualappearance of the image is not easily recognizable even if stored for along time.

The present invention provides a magenta ink set capable of suppressingchanges in the visual color balance due to the degradation of themagenta color in images even if stored for a long time.

The present invention also provides a recording unit and an inkcartridge which can be used very effectively for the production of inkjet color images in which image degradation due to the degradation ofthe magenta color in images is not easily noticeable.

According to one aspect of the present invention, there is provided anink set comprising a first aqueous ink and a second aqueous ink havingthe same color tone, wherein the first and second inks contain at leastone common coloring material, the second ink has a lower coloringmaterial content than the coloring material content of the first ink,and the degree of fading of an image produced with the second ink is thesame as or lower than the degree of fading of an image produced with thefirst ink.

According to another aspect of the present invention, there is providedan ink set comprising a first aqueous ink and a second aqueous inkhaving the same color tone, wherein the first and second inks contain atleast one common coloring material, the second ink has a lower coloringmaterial content than the coloring material content of the first ink,and the residual rate of the reflection density of an image producedwith the second ink when it is left under a condition that promotesfading is equal to or greater than that of an image produced with thefirst ink.

By using the ink sets as described above, it is possible to obtain colorimages in which the color balance does not become substantially unstableeven if the image is stored for a long time.

According to a further aspect of the present invention, there isprovided an ink jet recording apparatus comprising ink storage portionsstoring a first aqueous ink and a second aqueous ink having a same colortone respectively, wherein the first ink and the second ink contain atleast one common coloring material, the second ink has a lower coloringmaterial content than the coloring material content of the first ink,and the degree of fading of an image produced with the second ink is thesame as or lower than the degree of fading of an image produced with thefirst ink, and a head portion for ejecting the inks.

According to a further aspect of the present invention, there isprovided an ink jet recording apparatus comprising ink storage portionsstoring a first aqueous ink and a second aqueous ink having a same colortone respectively, wherein the first ink and the second ink contain atleast one common coloring material, the second ink has a lower coloringmaterial content than the coloring material content of the first ink,and the residual rate of the reflection density of an image producedwith the second ink when it is left under a condition that promotesfading is equal to or greater than that of an image produced with thefirst ink, and a head portion for ejecting the inks.

According to a further aspect of the present invention, there isprovided an ink jet recording method comprising the step of applying afirst aqueous ink and a second aqueous ink having the same color tone toa recording medium, wherein the first and second inks contain at leastone common coloring material, the second ink has a lower coloringmaterial content than the coloring material content of the first ink,and the degree of fading of an image produced with the second ink is thesame as or lower than the degree of fading of an image produced with thefirst ink.

According to a further aspect of the present invention, there isprovided an ink jet recording method comprising the step of applying afirst aqueous ink and a second aqueous ink having the same color tone toa recording medium, wherein the first ink and the second ink contain atleast one common coloring material, the second ink has a lower coloringmaterial content than that of the first ink, and the residual rate ofthe reflection density of an image produced with the second ink when itis left under a condition that promotes fading is equal to or greaterthan the residual rate of reflection density of an image produced withthe first ink when it is left under the same conditions.

By using the apparatuses and the methods as described above, it ispossible to obtain ink jet color images in which the color balance doesnot become substantially unstable even if stored for a long time.

According to a further aspect of the present invention, there isprovided an ink set comprising a first ink and a second ink having thesame color tone, wherein the second ink has a lower coloring materialcontent than the coloring material content of the first ink, the secondink is an aqueous ink containing a dye represented by the formula (I)below as a sole coloring material, and the first ink is an aqueous inkcontaining a dye represented by the formula (I) below and at least oneof a dye represented by the formula (II) below and a dye represented bythe formula (III) below, as coloring materials.

In formula (I), R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or 2.

In formula (II), Ar₁ is a substituted or unsubstituted phenyl group, ora substituted or unsubstituted naphthyl group; Ar₂ is selected from thegroup consisting of an acetyl group, a benzoyl group, a 1,3,5-triazinylgroup, a SO₂—C₆H₅ group, and a SO₂—C₆H₄—CH₃ group; and M is selectedfrom the group consisting of a hydrogen atom, an alkali metal, anammonium, and an organic ammonium, M being a counter ion of the sulfonicacid group.

In formula (III), each of Ar₃ and Ar₄ is independently a substituted orunsubstituted phenyl group, or a substituted or unsubstituted naphthylgroup, at least one of Ar₃ and Ar₄ having a carboxyl group or a saltthereof, or a sulfonic acid group or a salt thereof; M is selected fromthe group consisting of a hydrogen atom, an alkali metal, an ammonium,and an organic ammonium, M being a counter ion of the sulfonic acidgroup; R₅ is a 1,3,5-triazinediyl group; each of R₆ and R₇ isindependently selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkenyl group, a substituted or unsubstituted aralkyl group, and anatomic group necessary to complete a perhydroxyazine ring together withN; and L is a bivalent organic connecting group.

According to a further aspect of the present invention, there isprovided an ink set comprising a first ink and a second ink having thesame color tone, wherein the second ink has a lower coloring materialcontent than the coloring material content of the first ink, the secondink is an aqueous ink containing a dye represented by formula (I) as asole coloring material, and the first ink is an aqueous ink containing adye represented by formula (I) and at least one of C. I. Acid Red 52 andC. I. Acid Red 289.

By using the first and second inks containing the coloring materialsdescribed above, it is possible to obtain color images having superiordurability in which degradation over time due to the degradation of animage with magenta inks is inhibited.

According to a further aspect of the present invention, there isprovided an ink jet recording apparatus comprising ink storage portionsstoring a first ink and a second ink having a same color tonerespectively, wherein the second ink has a lower coloring materialcontent than the coloring material content of the first ink, the secondink is an aqueous ink containing a dye represented by formula (I) as asole coloring material, and the first ink is an aqueous ink containing adye represented by formula (I) and at least one of a dye represented byformula (II) and a dye represented by formula (III), as coloringmaterials, and a head portion for ejecting the inks.

According to a further aspect of the present invention, there isprovided an ink jet recording apparatus comprising ink storage portionsstoring a first ink and a second ink having a same color tonerespectively, wherein the second ink has a lower coloring materialcontent than the coloring material content of the first ink, the secondink is an aqueous ink containing a dye represented by formula (I) as asole coloring material, and the first ink is an aqueous ink containing adye represented by formula (I) and at least one of C. I. Acid Red 52 andC. I. Acid Red 289, and a head portion for ejecting the inks.

According to a further aspect of the present invention, there isprovided an ink jet recording method comprising the step of applying afirst ink and a second ink having the same color tone to a recordingmedium, wherein the second ink has a lower coloring material contentthan that of the first ink, the second ink is an aqueous ink containinga dye represented by formula (I) as a sole coloring material, and thefirst ink is an aqueous ink containing a dye represented by formula (I)and at least one of a dye represented by formula (II) and a dyerepresented by formula (III), as coloring materials.

According to a further aspect of the present invention, there isprovided an ink jet recording method comprising the step of applying afirst ink and a second ink having the same color tone to a recordingmedium, wherein the second ink has a lower coloring material contentthan that of the first ink, the second ink is an aqueous ink containinga dye represented by formula (I) as a sole coloring material, and thefirst ink is an aqueous ink containing a dye represented by formula (I)and at least one of C. I. Acid Red 52 and C. I. Acid Red 289, ascoloring materials.

By using the ink sets, the ink jet recording apparatuses, and the inkjet recording methods described above, it is possible to obtain ink jetcolor images having superior durability in which degradation of theimage over time due to the degradation of an image with the magenta inksis inhibited.

According to a still further aspect of the present invention, there isprovided a recording unit comprising an ink container section containinginks, and a head section for ejecting the inks, wherein the inksconstitute any one of the represented ink sets used for an ink jetprinter.

According to a still further aspect of the present invention, there isprovided an ink cartridge comprising an ink container section containinginks, wherein the inks constitute any one of the represented ink sets.

Further objects, features and advantages of the present invention willbecome apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a head section of an ink jetrecording apparatus;

FIG. 2 is a cross-sectional view taken along line 2—2 of FIG. 1;

FIG. 3 is a perspective view of a head section of an ink jet recordingapparatus;

FIG. 4 is a perspective view showing an ink jet recording apparatus;

FIG. 5 is a longitudinal sectional view of an ink cartridge;

FIG. 6 is perspective view of a recording unit;

FIG. 7 is a schematic diagram showing an ink cartridge in an embodimentof the present invention;

FIG. 8 is a schematic diagram showing a recording head provided with theink cartridge shown in FIG. 7;

FIG. 9 is a schematic diagram showing a recording unit in an embodimentof the present invention;

FIG. 10 is a schematic perspective view showing a key portion of an inkjet printer on which a liquid ejection head can be mounted;

FIG. 11 is a schematic perspective view showing an ink jet cartridgeprovided with a liquid ejection head;

FIG. 12 is a schematic perspective view showing a key portion of aliquid ejection head;

FIG. 13 is a conceptual diagram showing a portion of a liquid ejectionhead;

FIG. 14 is an enlarged view of an ejection port shown in FIG. 13;

FIG. 15 is a schematic diagram showing the ink adhesion state at theejection port shown in FIG. 14;

FIG. 16 is a schematic diagram showing a key portion of a liquidejection head;

FIG. 17 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time;

FIG. 18 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time;

FIG. 19 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time;

FIG. 20 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time;

FIG. 21 is a sectional view taken along the line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time;

FIG. 22 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time;

FIG. 23 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time; and

FIG. 24 is a sectional view taken along line 17—17 of FIG. 16, whichschematically shows the liquid ejection operation of the liquid ejectionhead with time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in more detail with reference tothe preferred embodiments.

In view of the technical background with respect to the related artdescribed above, the present inventors have carried out research inorder to produce ink jet color images having superior durability. It hasbeen found that fading proceeds more rapidly in a light color sectionhaving allow coloring material content; namely, with respect to an imageproduced by two inks having the same color tone with different coloringmaterial contents, even when coloring materials having the samelight-fastness are used for both inks, in the portion of the imageproduced using the light color ink, fading tends to become moreconspicuous than in the portion using the deep color ink. Consequently,the color balance becomes unstable in the whole image, and there tendsto be significant degradation of the visual appearance of the image.This tendency is particularly noticeable in the portions of the image inwhich light and deep magenta inks are used.

Furthermore, when a photo-like image is formed, in order to obtainsmooth gradation, the half tone portion of the image is usually formedusing a large amount of light color ink. As a method for maintaining thetone continuity between the deep color portion and the light colorportion, at least one common coloring material is contained in both thedeep color ink and the light color ink having different coloringmaterial contents. In contrast, the present inventors have found that inorder to improve the durability of an ink jet image in such a situation,it is important to bring the durability of an image produced by the deepcolor ink and the durability of an image produced by the light color inkinto balance. Namely, it is very important how the deep color ink andthe light color ink are combined. In a photo-like ink jet image in whichimage degradation is particularly easily noticeable, in order to furtherimprove the durability of the image, it is very important to discoverthe optimum combination of light and deep color inks. The presentinvention has been achieved based on such findings. In this context,fading means fading due to light.

Japanese Patent Laid-Open No. 2-127482 discloses a recording method forproviding images having superior light-fastness and clarity using knowninks having different coloring material contents, in which a deepmagenta ink and a light magenta ink contain different dyes. However, theabove-mentioned document does not describe the particular technicalproblems that arise when one common coloring material is contained inthe deep color ink and the light color ink in view of the tonecontinuity between the deep color portion and the light color portion,nor does it disclose any means for solving such problems. As a result ofresearch by the present inventors, it has been found that a magentacoloring material having an anthrapyridone skeleton represented byformula (I) exhibits light-fastness far exceeding that of the dye usedfor the light color ink disclosed in Japanese Patent Laid-Open No.2-127482, and even when the magenta coloring material is used for a deepcolor ink, images having both superior light-fastness and clarity areprovided.

Japanese Patent Laid Open Nos. 59-74173 and 2-16171, etc. disclosemagenta aqueous inks containing dyes having an anthrapyridone skeleton,and describe that the dyes have superior light-fastness. Japanese PatentLaid Open Nos. 57-197191 and 2000-169776 also disclose ink jet colorprinting methods using magenta aqueous inks containing dyes having ananthrapyridone skeleton. However, these documents do not disclose mixingof the anthrapyridone-based magenta dyes and other magenta dyes, andmoreover, do not even suggest improvement in light-fastness of imagesproduced by inks containing a mixture of a plurality of inks.Furthermore, the documents do not describe the attempt to make higherimage quality and improvement in light-fastness compatible with eachother by using two or more inks having the same color tone withdifferent image densities.

In a first embodiment of the present invention, when two inks havingdifferent coloring material contents are used for producing a colorimage, a first aqueous ink and a second aqueous ink are used. The firstink and the second ink have at least one common coloring material, thesecond ink has a lower coloring material content than that of the firstink, and the degree of fading of the second ink is the same as or lowerthan that of the first ink.

As described above, the present inventors have found that, with respectto an image produced by two inks having the same color tone withdifferent coloring material contents, fading proceeds more rapidly inthe light color section having a low coloring material content, and evenwhen coloring materials having the same light-fastness are used for bothinks, in the portion of the image produced using the light color ink,fading is more conspicuous. Consequently, the color balance becomesunstable in the whole image, and there tends to be significantdegradation of the visual appearance of the image. Therefore, in orderto inhibit this phenomenon, in the present invention, when an ink setincluding a first aqueous ink and a second aqueous ink having the samecolor tone and containing at least one common coloring material isprepared, the degree of fading of an image produced with the second inkhaving a low coloring material content is set to be the same as or lowerthan that of an image produced with the first ink having a high coloringmaterial content.

Herein, the meaning of “the degree of fading of an image produced withthe second ink is the same as or lower than that of an image producedwith the first ink” is that the fading rate of the image with the secondink is the same as or lower than that of the image with the first ink.

In a second embodiment of the present invention, when two inks havingdifferent coloring material contents are used for producing a colorimage, a first aqueous ink and a second aqueous ink are used. The firstink and the second ink contain at least one common coloring material,the second ink has a lower coloring material content than that of thefirst ink, and the residual rate of the reflection density of an imageproduced with the second ink when left under certain predeterminedconditions that promote fading is equal to or greater than the residualrate of the reflection density of an image produced with the first inkwhen left under such predetermined conditions. The residual rates of thereflection density of images produced with the first and second inks arepreferably 80% or more.

Herein, examples of the predetermined conditions that promote fadinginclude irradiation with a xenon lamp at approximately 6,000 klux·hr.That is, when ink images are left under such conditions, fading occursin the ink images, and reflection densities decrease, resulting invisual image degradation. Therefore, in the present invention, when anink set including a first aqueous ink and a second aqueous ink havingthe same color tone and containing at least one common coloring materialis prepared, a first ink having a high coloring material content and asecond ink having a low coloring material content are combined so that adecrease in the residual rate of the reflection density of an imageobtained by the second ink having a relatively low coloring materialcontent is equal to or greater than the decrease in the residual rate ofthe reflection density of an image obtained by the first ink having arelatively high coloring material content when left under certainconditions in which image degradation is likely to occur.

In order to satisfy such a relationship between the first and secondinks, an ink set in which coloring materials in the first and secondinks are appropriately selected may be used. For example, an ink set inwhich the first ink contains at least two coloring materials may beused. When the relevant ink set has a cyan tone, for example, as onecommon coloring material for the first and second inks, C. I. DirectBlue 199 may be used, and as another coloring material for the firstink, C. I. Acid Blue 9 may be used. Alternatively, C. I. Acid Blue 307may be used as one common coloring material, and as a second coloringmaterial for the first ink, C. I. Acid Blue 9 may be used.

When the relevant ink set has a yellow tone, for example, as one commoncoloring material for the first and second inks, C. I. Direct Yellow 86may be used, and as another coloring material for the first ink, C. I.Acid Yellow 23 may be used. Alternatively, C. I. Direct Yellow 132 maybe used as one common coloring material, and as another coloringmaterial for the first ink, C. I. Acid Yellow 23 may be used.

Next, ink sets having a magenta tone will be described below.

Coloring Material

Although the coloring material which can be used for the ink set in thepresent invention is not particularly limited, preferred examples of thecoloring materials include aqueous xanthene dyes, triphenylmethane dyes,anthraquinone dyes, monoazo dyes, disazo dyes, trisazo dyes, tetraazodyes, and copper phthalocyanine dyes, all of which are listed in theColor Index.

Preferred examples of the coloring material commonly used for the firstand second magenta inks include an anthrapyridone-based dye representedby formula (I) below.

In the formula (I), R₁ is a substituted or unsubstituted alkoxy group ora substituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or 2.

With respect to R₁ to R₄, more specifically, for example, R₁ is astraight-chain or branched alkoxy group with 1 to 4 carbon atoms, or asubstituted or unsubstituted phenyl group. Examples of the substitutedphenyl group include a methyl group, a hydroxyl group, a nitro group, asulfonic acid group or a salt thereof, a carboxyl group or a saltthereof, and a halogen atom, such as fluorine, chlorine, or bromine. Forexample, R₂ is a hydrogen atom, or a straight-chain or branched loweralkyl group with 1 to 4 carbon atoms, and R₃ is a hydrogen atom, astraight-chain or branched alkyl group with 1 to 4 carbon atoms, astraight-chain or branched alkoxy group with 1 to 4 carbon atoms, or anaryloxy group such as a phenoxy group. The aryl group constituting thearyloxy group may be, for example, replaced with a straight-chain orbranched alkyl group with 1 to 10 carbon atoms, a sulfonic acid group ora salt thereof, a carboxyl group or a salt thereof, or the like.Furthermore, for example, R₄ is a hydrogen atom, or a straight-chain orbranched lower alkyl group with 1 to 4 carbon atoms. Specific examplesof X₁ include —COOM, —SO₃M, where M is a hydrogen atom, an alkali metal,such as Li and Na, an ammonium (NH₄), and an organic ammonium (N(R₈)₄),where R₈ is a methyl group, an ethyl group, or the like.

Examples of dyes which can be used for adding to the first ink togetherwith the coloring materials described above include a xanthene dye, suchas at least one dye selected from the group consisting of C. I. Acid Red52, C. I. Acid Red 289, etc., and at least one dye selected from thedyes represented by formulae (II) and (III) below, or both. Inparticular, when a dye represented by formula (I), a dye represented byformula (II), and C. I. Acid Red 289 are combined as coloring materialsin the first ink, the image produced with the ink has a superior magentacolor tone, which is, coupled with the effect of inhibiting a change incolor balance, particularly advantageous for the formation of photo-likecolor images.

In formula II, Ar₁ is a substituted or unsubstituted phenyl group, or asubstituted or unsubstituted naphthyl group; Ar₂ is selected from thegroup consisting of an acetyl group, a benzoyl group, a 1,3,5-triazinylgroup, a SO₂—C₆H₅ group, and a SO₂—C₆H₄—CH₃ group; and M is selectedfrom the group consisting of a hydrogen atom, an alkali metal such as Liand Na, an ammonium (NH₄), and an organic ammonium (N(R₉)₄), where R₉ isa methyl group, an ethyl group, or the like, M being a counter ion ofthe sulfonic acid group. The phenyl group or the naphthyl group of Ar₁may be replaced with, for example, at least one group or atom selectedfrom the group consisting of a carboxyl group or a salt thereof, asulfonic acid group or a salt thereof, a straight-chain or branchedalkyl group with 1 to 4 carbon atoms, a halogen atom, such as fluorine,chlorine, or bromine, an alkoxy group with 1 to 4 carbon atoms, and anaryloxy group, such as a phenoxy group. When Ar₂ is a benzoyl group or a1,3,5-triazinyl group, at least one hydrogen atom in the benzene ring orthe 1,3,5-triazine ring may be replaced with a carboxyl group or a saltthereof, a halogen atom, such as fluorine, chlorine, or bromine, aprimary amino group, a secondary amino group, a tertiary amino group, analkoxy group, a hydroxyl group, or the like.

In formula III, each of Ar₃ and Ar₄ is independently a substituted orunsubstituted phenyl group, or a substituted or unsubstituted naphthylgroup. Examples of the substituted phenyl group and naplithyl groupinclude a straight-chain or branched alkyl group with 1 to 4 carbonatoms, a straight-chain or branched alkoxyl group with 1 to 4 carbonatoms, a hydroxyl group, a carboxyl group or a salt thereof, a sulfonicacid group or a salt thereof, and a halogen atom, such as fluorine,chlorine, or bromine. At least one of Ar₃ and Ar₄ has a carboxyl groupor a salt thereof, or a sulfonic acid group or a salt thereof. M isselected from the group consisting of a hydrogen atom, an alkali metalsuch as Li and Na, an ammonium (NH₄), and an organic ammonium (N(R₁₀)₄),where R₁₀ is a methyl group, an ethyl group, or the like, M being acounter ion of the sulfonic acid group. R₅ is a 1,3,5-triazinediylgroup, at least one hydrogen atom in the 1,3,5-triazine ring may bereplaced with a carboxyl group or a salt thereof, a halogen atom, suchas fluorine, chlorine, or bromine, a primary amino group, a secondaryamino group, a tertiary amino group, an alkoxy group, a hydroxyl group,or the like. Each of R₆ and R₇ is independently selected from the groupconsisting of a hydrogen atom, a substituted or unsubstituted alkylgroup, a substituted or unsubstituted alkenyl group, a substituted orunsubstituted aralkyl group, and an atomic group necessary to complete aperhydroxyazine ring together with N. L is a bivalent organic connectinggroup. Specific examples of R₆ and R₇ include a straight-chain orbranched alkyl group with 1 to 6 carbon atoms, a straight-chain orbranched alkenyl group with 1 to 4 carbon atoms, and a benzyl group.Examples of the substituents of the alkyl group, the alkenyl group, andthe benzyl group include a hydroxyl group, a carboxyl group or a saltthereof, and a sulfonic acid group or a salt thereof.

As specific examples of the first coloring material represented byformula (I), which are preferably used in the present invention,illustrative compounds I-1 to I-7 are shown below. However, the presentinvention is not limited to these coloring materials. Two or more ofthese coloring materials may be used simultaneously.

Specific examples of the compounds represented by the formula (II),which are preferably used as coloring materials in the presentinvention, include C. I. Reactive Red 180, illustrative compounds II-8to II-13 of which structures are shown below, and compounds of whichstructures are shown in Japanese Patent Laid-Open Nos. 8-73791 and11-209673.

Examples of the compounds represented by formula (III), which arepreferably used as coloring materials in the present invention, includeillustrative compounds III-14 to III-22, of which the structures areshown below.

In the first magenta ink, the weight ratio of the coloring materialrepresented by formula (1) to the rest of the coloring material ispreferably set in the range of 95:5 to 20:80 in consideration of theadvantage that clear tones, high image densities, and superiorlight-fastness are obtained.

Additionally, with respect to the individual inks used in the presentinvention, regardless of the color tones of the inks, in the deep colorink of the first ink having a high coloring material content, the totalcontent of all coloring materials in the ink is preferably 1.0% to 15.0%by weight of the total amount of the first ink, and in the light colorink of the second ink having a low coloring material content, the totalcontent of all coloring materials in the ink is preferably 0.1% to 5.0%by weight of the total amount of the second ink.

Aqueous Medium

The individual inks used in the present invention are aqueous inkscontaining the coloring materials as described above and aqueous media,which may contain a water-soluble organic solvent. The water-solubleorganic solvent contained in the aqueous medium used is not particularlylimited. Examples of the water-soluble organic solvent include alcohols,polyhydric alcohols, polyglycols, glycol ethers, polar solventscontaining nitrogen, and polar solvents containing sulfur. The contentof these water-soluble solvents in the ink is preferably 1% to 40% byweight of the total amount of ink, and more preferably, 3% to 30% byweight, in consideration of maintenance of moisture in the ink,improvement in the solubility of the coloring materials, effectivepermeation of the ink into the recording paper, etc. The content ofwater in the ink is preferably 30% to 95% by weight so that satisfactorysolubility of the dyes as coloring materials in the ink is exhibited,sufficient viscosity of the ink for stable ink ejection is exhibited,and clogging does not occur at nozzles.

pH

The pH of each ink used in the present invention is not particularlylimited, as long as the solubility of the coloring materials issatisfied. However, in view of safety, etc., the preferred pH is in therange of 4.0 to 11.0.

Additives

When the individual inks used in the present invention are prepared, inorder to maintain moisture in the ink, moisture-maintainingconstituents, such as urea, urea derivatives, and trimethylolpropane,may be used as ink constituents. The content of suchmoisture-maintaining constituents in the ink is preferably 0.1% to 20.0%by weight of the total amount of the ink, and more preferably, 3.0% to10.0% by weight. Furthermore, the individual inks used in the presentinvention may further contain, as necessary, other various additives,such as surfactants, pH regulators, rust preventives, preservatives,mildew-proofing agents, antioxidants, anti-reducing agents, evaporationaccelerators, chelating agents, and water-soluble polymers.

The inks used for the ink sets in the embodiments of the presentinvention are particularly suitable for an ink jet recording method inwhich recording is performed by the ejection of liquid droplets by theaction of thermal energy. Of course, the inks may also be used for othertypes of ink jet recording methods and for general writing implements.

Recording Apparatus, Ink Cartridge, and Recording Unit

As a suitable recording apparatus for performing recording using the inkset of the present invention, an ink jet recording apparatus of thepresent invention may be mentioned, in which thermal energy in responseto recording signals is applied to inks stored in chambers of arecording head, and liquid droplets are generated.

FIGS. 1 to 3 show structural examples of recording heads.

A head 13 includes a plate composed of glass, ceramic, or plasticprovided with an ink passage 14, and a heat generation head 15 bondedthereto. The heat generation head 15 includes a protective film 16composed of a silicon oxide or the like, aluminum electrodes 17-1 and17-2, heat generation resistor layer 18 composed of nichrome or thelike, a heat accumulation layer 19, and a substrate 20 composed of amaterial with satisfactory heat dissipation, such as alumina. An ink 21is filled up to an ink ejection orifice (fine port) 22, and a meniscus23 is formed due to pressure. When an electrical signal is applied tothe electrodes 17-1 and 17-2, an area n rapidly generates heat, creatingbubbles in the ink 21 in contact with the area n. The meniscus 23 isdischarged through the orifice 22 to form recording liquid droplets 24,which are ejected toward a recording medium 25. FIG. 3 shows a schematicdiagram of a recording head provided with multiple passages 26 in whichmany nozzles, each as shown in FIG. 1, are arrayed. The recording headis fabricated by bonding a glass plate 27 provided with many passagesand a heat generation head 28, which is similar to that described withreference to FIG. 1, together. Additionally, FIG. 1 is a sectional viewof the head 13 taken along the ink passage, and FIG. 2 is a sectionalview taken along line 2—2 of FIG. 1.

FIG. 4 is a perspective view showing an example of an ink jet recordingapparatus in which a head as described above is used. A blade 61, whichacts as a wiping member, has a cantilever structure in which one end isheld by a blade-holding member. The blade 61 is disposed adjacent to theregion recorded by the recording head, and is held so as to protrude inthe moving course of the recording head. A cap 62 is disposed at thehome position adjacent to the blade 61, and moves in a directionperpendicular to the moving direction of the recording head and abutsthe ejection surface for performing capping. An ink absorbent 63 is heldso as to protrude in the moving course of the recording head in the samemanner as that of the blade 61.

The blade 61, the cap 62, and the ink absorbent 63 constitute anejection recovery section 64, and moisture, dust, etc. on the inkejection surface are removed by the blade 61 and the absorbent 63.

Numeral 65 represents a recording head having an ejection energygeneration means for ejecting an ink to a recording medium facing theejection surface and is provided with an ejection port. Numeral 66represents a carriage for carrying the recording head 65. The carriage66 is slidably engaged with a guide shaft 67, and a part of the carriage66 is connected to a belt 69 driven by a motor 68. Thereby, the carriage66 moves along the guide shaft 67 so that the recording head 65 moves inthe recording region and its adjacent region.

Numeral 51 represents a paper feed section for inserting-the recordingmedium, and numeral 52 represents a feed roller driven by a motor notshown in the drawing. In such a structure, the recording medium is fedto a position facing the ejection surface of the recording head 65, andas recording progresses, the recording medium is sent to the dischargesection provided with discharge rollers 53.

In the structure described above, when the recording head 65 returns tothe home position after recording is completed, although the cap 62 ofthe ejection recovery section 64 retreats from the moving path of therecording head 65, the blade 61 protrudes toward the moving path.Consequently, the ejection surface of the recording head 65 is wiped.Additionally, when the cap 62 performs capping while abutting on theejection surface of the recording head 65, the cap 62 moves so as toprotrude toward the moving path of the recording head 65.

When the recording head 65 moves from the home position to the startingposition for recording, the cap 62 and the blade 61 are located at thesame positions as those during wiping. Consequently, the ejectionsurface of the recording head 65 is also wiped when the recording head65 moves in such a way. Additionally, while the recording head 65 movesin the recording region for performing recording, the recording head 65moves to the home position adjacent to the recording region atpredetermined intervals, and wiping is also performed during such amove.

FIG. 5 is a sectional view showing an ink cartridge 45 which containsink to be supplied to a head, for example, via a tube. The ink cartridge45 includes an ink bag 40 as an ink container section, and a stopper 42composed of rubber provided on the tip of the ink bag 40. The ink in theink bag 40 can be supplied to the head by inserting a needle (not shownin the drawing) into the stopper 42. Numeral 44 represents an inkabsorbent for absorbing waste ink. In the preset invention, each of thefirst ink and the second ink is filled in the ink container section ofsuch an ink cartridge, and each ink cartridge is mounted on an ink jetprinter provided with an ink jet recording head for ejecting theindividual inks, and image formation is performed, and thereby thesuperior effects of the present invention are achieved.

FIG. 7 shows an ink cartridge in another embodiment of the presentinvention, in which the first ink and the second ink constituting theink set of the present invention are separately filled. A cartridge 701includes two container sections 703 and 705 for containing the first inkand the second ink, respectively, and the cartridge 701 is detachablyfitted into an ink jet head 801 for ejecting the individual inksseparately, as shown in FIG. 8. When the cartridge 701 is fitted into arecording head 801, two types of ink having different coloring materialcontents are supplied to the recording head 801.

The ink jet recording apparatus of the present invention is not limitedto the one described above in which the recording head and the inkcartridge are separately provided. An ink jet recording apparatus inwhich a recording head and an ink cartridge are integrated, as shown inFIG. 6, is also preferably used.

In FIG. 6, a recording unit 70 includes ink container sections in whichthe individual inks constituting the ink set of the present invention,for example, ink absorbents are contained, and the inks in the inkabsorbents are ejected from a head section 71 provided with a pluralityof orifices. An air communicating opening 72 connects the interior ofthe recording unit 70 with air. The recording unit 70 can be usedinstead of the recording head 65 shown in FIG. 4, and is detachablymounted on the carriage 66.

Furthermore, a recording unit in another embodiment of the presentinvention will be described, in which the first ink and the second inkconstituting the ink set of the present invention are contained in therespective ink container sections in an ink tank, and the ink tank and arecording head for ejecting the individual inks are integrally provided.Specifically, as shown in FIG. 9, a recording unit 907 includes acontainer section 901 for containing the first ink, a container section903 for containing the second ink, and a recording head 905 in which inkpassages are separately provided so that the individual inks areseparately ejected.

Additionally, although the ink jet recording apparatus in which inkdroplets are ejected by applying thermal energy to ink has beendescribed above, the present invention is also applicable to an ink jetrecording apparatus in which a piezoelectric element is used.

Next, other examples of the recording apparatus and the recording headwhich are preferably used in the present invention will be described.

FIG. 10 is a schematic perspective view showing a liquid ejection head,in which bubbles are completely surrounded by air during ejection, and akey portion of an ink jet printer as a liquid ejection apparatus usingthe liquid ejection head. The ink jet printer shown in FIG. 10 includesa casing 1008 containing a conveying device 1030 for intermittentlyconveying a recording sheet 1028 (recording medium), which is providedlengthwise, in the P direction shown in the drawing; a recording device1010 which is reciprocated along a guide shaft 1014 in a directionsubstantially orthogonal to the conveying direction P of the recordingsheet 1028 by the conveying device 1030; and a movement driving device1006 as a driving means for reciprocating the recording device 1010.

The conveying device 1030 includes a pair of rollers 1022 a and 1022 b,a pair of rollers 1024 a and 1024 b, and a driving unit 1020 for drivingthe individual pairs of rollers. When the driving unit 1020 is operated,the recording sheet 1028 is intermittently conveyed in the P directionwhile being sandwiched between the rollers 1022 a and 1022 b and betweenthe rollers 1024 a and 1024 b.

The movement driving device 1006 includes a belt 1016 placed aroundpulleys 1026 a and 1026 b rotatably disposed with a predetermineddistance therebetween; and a motor 1018 for driving the belt 1016, whichis placed substantially parallel to the rollers 1022 a and 1022 b and isconnected with a carriage member 1010 a of the recording device 1010, inthe forward direction and the reverse direction.

When the motor 1018 is operated and the belt 1016 is rotated in the Rdirection shown in FIG. 10, the carriage member 1010 a of the recordingdevice 1010 is moved in the S direction by a predetermined length. Whenthe motor 1018 is operated and the belt 1016 is rotated in a directionopposite to the R direction, the carriage member 1010 a of the recordingdevice 1010 is moved in a direction opposite to the S direction by apredetermined length. Furthermore, on one end of the movement drivingdevice 1006, a recovery unit 1026 for performing ejection recoverytreatment on the recording device 1010 is provided facing the inkejection port array of the recording device 1010.

The recording device 1010 is provided with ink jet cartridges(hereinafter may be referred to as cartridges) 1012Y, 1012M, 1012C, and1012B corresponding to yellow, magenta, cyan, and black, each detachablyplaced in the carriage member 1010 a.

FIG. 11 shows an ink jet cartridge which is mountable on the ink jetrecording apparatus described above in an embodiment of the presentinvention. A cartridge 1012 is of a serial type, and includes an ink jetrecording head (liquid ejection head) 100 and a liquid tank 1001 forcontaining liquid, such as inks. The ink jet recording head 100 isprovided with a plurality of ejection ports 832 for ejecting liquid, andliquid, such as ink, is guided to a common liquid chamber (refer to FIG.12) of the liquid ejection head 100 via liquid supply passages (notshown in the drawing). In the cartridge 1012 shown in FIG. 11, the inkjet recording head 100 and the liquid tank 1001 are integrated, andliquid is supplied from the liquid tank 1001 as necessary. However, theliquid tank 1001 may be detachably connected to the liquid ejection head100.

The liquid ejection head which is mountable on the ink jet printer asdescribed above will be described in more detail.

FIG. 12 is a schematic perspective view showing a key portion of aliquid ejection head in an embodiment of the present invention, andFIGS. 13 to 15 are schematic diagrams showing the shape of the ejectionport section of the liquid ejection head shown in FIG. 12. Electricalwiring for driving electrothermal converting elements, etc. is omittedin the drawing.

As shown in FIG. 12, in the liquid ejection head, a substrate 934composed of glass, ceramic, plastic, metal, or the like is used. Thematerial for the substrate 934 is not particularly limited as long as itfunctions as a part of a liquid-passage-constituting member and as asupport for ink ejection energy generation elements and a material layerfor forming liquid passages and ejection ports. In this embodiment, asilicon substrate (wafer) is used as the substrate 934. The ejectionports may be formed by laser irradiation or by an aligner, such as amirror projection aligner (MPA), using an orifice plate (ejection portplate) 935 composed of a photosensitive resin.

As shown in FIG. 12, the substrate 934 is provided with electrothermalconverting elements (hereinafter may be referred to as heaters) 931 andan ink supply port 933, which is a through-hole shaped like a longgroove, as a common liquid chamber. Heaters 931 acting as thermal energygeneration means are arrayed in a zigzag line on each side of the inksupply port 933, for example, with a separation of 300 dpi betweenheaters. The substrate 934 is provided with ink passage walls 936 forforming ink passages. The ejection plate 935 provided with ejectionports 832 is disposed on the ink passage walls 936.

Although the ink passage walls 936 and the ejection plate 935 areseparate members in the embodiment shown in FIG. 12, the ink passagewalls 936 and the ejection plate 935 may be integrally formedsimultaneously by spin coating or the like. In this embodiment, theupper surface 935 a of the ejection plate 935 is subjected towater-repellent finishing.

In this embodiment, a serial type head, which performs recording whilescanning in the S direction shown in FIG. 10, is used and recording isperformed, for example, at 1,200 dpi. The drive frequency is 10 kHz, andejection is performed at minimum time intervals of 100 μs. As shown inFIG. 13, division walls 936 a for isolating fluids ejected by adjacentnozzles have a width W of 14 μm. As shown in FIG. 16, liquid flow path1338 has a bubble generation chamber 1337 formed by the ink passage wall936 with a width N₁ of 33 μm and a length N₂ of 35 μm. The heater 931has a size of 30 μm×30 μm, the heater resistance is 53 Ω, and the drivevoltage is 10.3 V. The ink passage wall 936 and the division wall 936 ahave a height of 12 μm and the orifice plate 935 has a thickness of 11μm.

FIG. 14 is a sectional view of an ejection port 832 in an ejection portsection 940 shown in FIG. 12, taken in a direction orthogonal to thedirection in which ink is ejected (the thickness direction of theorifice plate 935). As shown in FIG. 14, the cross section of theejection port 832 is substantially star-shaped, and includes 6 convexsections 832 a with obtuse angles, and 6 concave sections 832 b withacute angles. The convex sections 832 a and the concave sections 832 bare arranged alternately. That is, 6 grooves 1141 are formed in thethickness direction of the orifice plate 935 (in the liquid ejectiondirection). The concave sections 832 b, which are further from thecenter O of the ejection port, correspond to the distal portions of thegrooves 1141, and the convex sections 832 a, which are closer to thecenter O of the ejection port, correspond to the proximal portions ofthe grooves 1141, as shown in FIG. 14.

In this embodiment, for example, the ejection port section 940 has across section with a shape in which an equilateral triangle having sidesof 27 μm is laid over a similar triangle and rotated by an angle of 60degrees. The length T₁ shown in FIG. 14 is 8 μm. Each convex section 832a has an angle of 120 degrees, and each concave section 832 b has anangle of 60 degrees. Therefore, the center O of the ejection portcorresponds to the median point G of a polygon formed by linkingtogether the centers of the adjacent grooves, i.e., centers (medianpoints) of figures formed by linking the distal points of the grooveswith the two proximal points adjacent to the distal point. The openingarea of the ejection port 832 is 400 μm², and the opening area of onegroove 1141 (the area of the figure formed by linking the distal pointof the groove with the two proximal points adjacent to the distal point)is approximately 33 μm². FIG. 15 is a schematic diagram showing thestate of the adhesion ink (C) at the ejection port shown in FIG. 14.

Next, the liquid ejection operation by the ink jet recording head havingthe structure described above will be described with reference to FIGS.17 to 24. FIGS. 17 to 24 are sectional views of the bubble generationchamber 1337, taken along the line 17—17 of FIG. 16. In the drawings,the end of the ejection port section 940 in the thickness direction ofthe orifice plate 935 corresponds to the top part 1141 a of the groove1141. FIG. 17 shows a state in which a film-like bubble is generated inthe liquid or ink, designated as I, on the heater 931, FIGS. 18 to 24show the states at approximately 1 μs, 2 μs, 3 μs, 4 μs, 5 μs, 6 μs, and7 μs after the state shown in FIG. 17, respectively. Additionally, theword “fall” or “sink” in the description below means movement toward theelectrothermal converting element 931 regardless of the mountingdirection of the head, and does not mean a fall in the direction ofgravity.

First, as shown in FIG. 17, as electric current is applied to the heater931 based on a recording signal, etc., a bubble 101 is generated in aliquid passage 1338 above the heater 931, and at approximately 1 to 2μs, the bubble 101 rapidly grows due to thermal expansion, as shown inFIGS. 18 and 19. When the bubble 101 is at its largest, the height ofthe bubble 101 exceeds the height of the ejection port surface 935 a,and at this stage, the pressure of the bubble decreases from theatmospheric pressure by several to several tens percent.

Next, approximately 2 μs after the generation of the bubble 101, thevolume of the bubble 101 starts decreasing from the maximum, and almostsimultaneously, generation of a meniscus 102 starts. As shown in FIG.20, the meniscus 102 retreats, i.e., falls, toward the heater 931. Inthis embodiment, as described above, since the ejection port section hasa plurality of grooves 1141, when the meniscus 102 retreats, capillaryattraction acts on the groove 1141 in the F_(C) direction opposite tothe retreating direction F_(M) of the meniscus 102. As a result, even ifvariations occur in the state of the bubble 101 for some reason, whenthe meniscus 102 retreats, the shapes of the meniscus 102 and a mainliquid droplet (hereinafter may be referred to as liquid or ink) I_(a)are corrected so as to be substantially symmetrical with respect to thecenter of the ejection port.

Since the falling rate of the meniscus 102 is higher than thecontraction rate of the bubble 101, as shown in FIG. 21, approximately 4μs after the generation of the bubble, the bubble 101 separates from thelower surface of the ejection port 832 and is completely surrounded byair. At this stage, liquid (ink) in the vicinity of the central axis ofthe ejection port 832 sinks toward the heater 931. This is due to thefact that the liquid (ink) I_(a) which is pulled back toward the heater931 by a negative pressure of the bubble 101 before the bubble isconnected to air still maintains the velocity toward the heater 931 dueto inertia. As shown in FIG. 22, the liquid (ink) sinks toward theheater 931, reaches the surface of the heater 931 approximately 5 μsafter the generation of the bubble 101, and as shown in FIG. 23, theliquid spreads over the surface of the heater 931.

The lower portion of the liquid spreading over the surface of the heater931 as described above has a vector directed along the surface of theheater 931, but loses a vector orthogonal to the surface of the heater931, such as a vector directed normal to the surface of the heater 931,and stays on the surface of the heater 931, thereby pulling down theupper portion of the liquid, i.e., the liquid having a velocity vectordirected in the ejection direction. Subsequently, liquid I_(b) betweenthe lower portion of the liquid spreading over the heater 931 and theupper portion of the liquid (main liquid droplet) I_(a) becomes thinner,and as shown in FIG. 24, the liquid I_(b) is cut in the center of thesurface of the heater 931 approximately 7 μs after the generation of thebubble 101, and thus the main liquid droplet I_(a) having a velocityvector directed in the ejection direction is separated from liquid I_(c)spreading over the surface of the heater 931. As described above, theposition of the separation is preferably in the liquid passage 1338, andmore preferably, at the side of the electrothermal converting element(heater) 931 rather than at the side of the ejection port 832.

The main liquid droplet I_(a) is ejected from the center of the ejectionport 832 and hits a predetermined position on the surface of therecording medium, without a slant in the ejection direction. In aconventional liquid ejection head, the liquid I_(c) spreading over thesurface of the heater 931 is ejected as a satellite droplet after themain liquid droplet. However, in the present invention, the liquid I_(c)spreading over the surface of the heater 931 remains on the surface ofthe heater 931 and is not ejected. In such a way, since it is possibleto inhibit the ejection of the satellite droplet, spray which is likelyto occur due to the ejection of the satellite droplet can be avoided,and thus it is possible to reliably prevent the surface of the recordingmedium from being smeared by this spray. Additionally, in FIGS. 22 to24, symbol I_(d) represents ink adhering to the groove (ink inside thegroove) and symbol I_(e) represents ink remaining in the liquid passage.

As described above, in the liquid ejection head in this embodiment, whenthe liquid is ejected after the bubble grows largest and the volume ofthe bubble decreases, the direction of the main liquid droplet can bestabilized by a plurality of grooves arranged around the center of theejection port. Consequently, it is possible to provide a liquid ejectionhead which ejects the liquid without a slant so that the liquid hits therecording medium accurately. Since it is also possible to stably ejectthe liquid with respect to variations in bubbling at high drivefrequencies, high speed, high definition printing is enabled.

In particular, since the liquid is ejected by completely surrounding thebubble by air for the first time at the stage in which the volume of thebubble decreases, it is possible to prevent spray from occurring whenthe liquid droplet is ejected. Consequently, it is possible to preventthe liquid droplet from adhering to the ejection port surface, which maycause sudden non-ejection. Examples of the recording head in whichbubbles are completely surrounded by air during ejection, which can befavorably used in the present invention, include a so-called “edgeshooter type” recording head, such as the one disclosed in JapanesePatent No. 2783647.

Next, the present invention will be described in more detail withreference to Examples and Comparative Examples. The contents of the inkingredients in the Examples and Comparative Examples are shown in partsby weight unless otherwise indicated.

EXAMPLES 1 TO 7 AND COMPARATIVE EXAMPLES 1 TO 6

The coloring materials and deionized water shown in Table 1 or 2 belowwere added to the ingredients shown in the ink composition 1 below so asto make the total 100 parts, followed by mixing. Using a 0.20 μm filter,pressure filtration was performed, and ink sets in Examples 1 to 7 andComparative Examples 1 to 6, each containing two inks having differentcoloring material contents, were prepared.

Ink Composition 1 Glycerol  5.0 parts by weight Urea  5.0 parts byweight Diethylene Glycol 10.0 parts by weight Acetylenol EH(manufactured by Kawaken  0.3 part by weight Fine Chemicals Co., Ltd.)Ethanol  5.0 parts by weight

TABLE 1 Example 1 Example 2 Example 3 Example 4 C1 C1 C2 C2 Y1 Y1 Y2 Y2Light Deep Light Deep Light Deep Light Deep C.I. Acid 0.5 0.3 Blue 9C.I. Direct 1.5 3.5 Blue 199 C.I. Direct 2.0 3.5 Blue 307 C.I. Acid 0.51.0 Yellow 23 C.I. Direct 1.2 2.5 Yellow 132 C.I. Direct 1.0 2.5 Yellow86 C.I. Acid Red 289 Deionized 73.2 70.7 72.7 70.9 73.7 71.7 73.5 71.2water Example 5 Example 6 Example 7 M1 M1 M2 M2 M3 M3 Light Deep LightDeep Light Deep Illustrative 2.2 Compound I-3 Illustrative 1.0 1.5 2.5Compound I-2 Illustrative 1.8 3.0 Compound I-7 Illustrative 1.0 CompoundII-8 Illustrative 1.6 Compound II-12 Illustrative 1.5 Compound III-21C.I. Acid Red 0.1 289 Deionized water 73.7 70.9 73.2 70.7 72.9 70.6

TABLE 2 Comparative Comparative Comparative Comparative ComparativeComparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6C3 C3 C4 C4 Y3 Y3 Y4 Y4 M4 M4 M5 M5 Light Deep Light Deep Light DeepLight Deep Light Deep Light Deep C.I. Acid 1.5 4.0 Blue 9 C.I. Direct2.0 3.8 Blue 307 C.I. Acid 1.0 1.0 Yellow 23 C.I. Direct 2.0 Yellow 132C.I. Direct 1.0 3.5 Yellow 86 Illustrative 1.5 4.0 Compound I-7Illustrative 0.9 3.8 Compound II-8 Deionized 73.2 70.7 72.7 70.9 73.771.7 73.7 71.2 73.8 70.9 73.2 70.7 waterEvaluation

With respect to each of the ink sets obtained in Examples 1 to 7 andComparative Examples 1 to 6, printing was performed using an on-demandtype ink jet printer having heat generation elements as energy sourcesfor ejecting ink. The resulting printed images were evaluated withrespect to (1) light-fastness and (2) color developing ability under theconditions described below. The results thereof are shown in Table 3.

(1) Light-Fastness

A deep color ink having a higher coloring material content and a lightcolor ink having a lower coloring material content constituting the inkset in each of the Examples and Comparative Examples were fitted intothe printer, and using the individual inks, solid images were printed ontwo recording media, i.e., a PPC paper (manufactured by Canon KabushikiKaisha) and a glossy paper (PR-101 manufactured by Canon KabushikiKaisha). The printed materials thus obtained were air-dried for 24hours, and using a xenon fade-meter Ci3000 (manufactured by Atlas Co.)provided with an ultraviolet cut filter, irradiation was performed for100 hours at a vessel temperature of 35° C., a humidity of 60% RH, andan irradiation intensity of 60 klux. The solid images of the printedmaterials were measured with a Macbeth Densitometer RD-918 before andafter the irradiation to find the residual rate of the reflectiondensity, and the light-fastness was evaluated based on the followingstandards.

(1-a)

A: The residual rate of the reflection density of the image produced bythe deep color ink was 80% or more.

B: The residual rate of the reflection density of the image produced bythe deep color ink was 60% or more to less than 80%.

C: The residual rate of the reflection density of the image produced bythe deep color ink was less than 60%.

(1-b)

A: The residual rate of the reflection density of the image produced bythe light color ink was equal to or higher than the residual rate of thereflection density of the image produced by the deep color ink.

B: The residual rate of the reflection density of the image produced bythe light color ink was lower than the residual rate of the reflectiondensity of the image produced by the deep color ink.

(2) Color Developing Ability

The deep color ink having a higher coloring material content in each inkset was fitted into the printer, and solid images were printed on tworecording media, i.e., a PPC paper (manufactured by Canon KabushikiKaisha) and a glossy paper (PR-101 manufactured by Canon KabushikiKaisha). The printed materials thus obtained were air-dried for 24hours, and the color developing ability thereof was visually checkedbased on the following standards.

AA: The color tone was significantly clear.

A: The color tone was clear.

B: The color tone was slightly dull.

TABLE 3 Light-fastness (2) (1-a) (1-b) Color Deep Color Light ColorDeveloping Ink Ink Ability Example 1 A A A Example 2 A A A Example 3 A AA Example 4 A A A Example 5 A A A Example 6 A A A Example 7 A A AAComparative C B A Example 1 Comparative A B B Example 2 Comparative B BA Example 3 Comparative A B B Example 4 Comparative B B A Example 5Comparative A B B Example 6

Furthermore, using the inks in Examples 1 to 7, the printed materialsused for the light-fastness evaluation were visually observed before andafter the irradiation test. As a result, fading was not noticeableeither in the portion printed with the first ink having a relativelyhigh coloring material content or in the portion printed with the secondink having a relatively low coloring material content. In contrast, withrespect to the printed materials used in Comparative Examples 1 to 6,since a change in color tone was partially observed due to the fading ofthe portion printed with the second ink, fading of the images after thetest was noticeable. Consequently, it was found that in the presentinvention, the difference in deterioration rate due to light irradiationbetween the portion printed with the first ink and the portion printedwith the second ink was relieved or overcome. It is obvious from theresults described above that, in images produced with the first andsecond inks constituting the ink set of the present invention, a changeover time in color balance due to a difference in deterioration rate canbe inhibited.

While the present invention has been described with reference to whatare presently considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

1. A second aqueous ink for an ink jet recording apparatus used with afirst aqueous ink, comprising a dye as a coloring material; wherein thesecond aqueous ink and the first aqueous ink contain at least one commondye, the second aqueous ink has a same color tone as the first aqueousink, the second aqueous ink has a lower dye content than the dye contentof the first aqueous ink, and a degree of fading of an image producedwith the second aqueous ink is the same as or lower than a degree offading of an image produced with the first aqueous ink.
 2. A secondaqueous ink according to claim 1, wherein the color tone is magenta. 3.A second aqueous ink for an ink jet recording apparatus used with afirst aqueous ink, comprising a dye as a coloring material, wherein thesecond aqueous ink and the first aqueous ink contain at least one commondye, the second aqueous ink has a same color tone as the first aqueousink, the second aqueous ink has a lower dye content than the dye contentof the first aqueous ink, and, a residual rate of reflection density ofan image produced with the second aqueous ink is the same as or greaterthan a residual rate of reflection density of an image produced with thefirst aqueous ink.
 4. A second aqueous ink according to claim 3, whereinthe color tone is magenta.
 5. A second aqueous ink according to claim 1,wherein each degree of the fading of the images produced with the firstaqueous ink and the second aqueous ink is equal to or greater than 80%residual rate of reflection density of the image.
 6. A second aqueousink according to claim 5, wherein the residual rate of reflectiondensity of the image is obtained by irradiation with a xenon lamp at6,000 klux·hr.
 7. A second aqueous ink according to claim 1, wherein thecolor tone is cyan.
 8. A second aqueous ink according to claim 3,wherein each residual rate of the reflection density of the imagesproduced with the first aqueous ink and the second aqueous ink is equalto or greater than 80%.
 9. A second aqueous ink according to claim 8,wherein the condition includes irradiation with a xenon lamp at 6,000klux·hr.
 10. A second aqueous ink according to claim 3, wherein thecolor tone is cyan.
 11. A second aqueous ink according to claim 2,wherein the second aqueous ink contains a dye represented by formula (I)as a sole coloring maternal:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof and n is 1 or
 2. 12. A second aqueous inkaccording to claim 4, wherein the second aqueous ink contains a dyerepresented by formula (I) as a sole coloring material:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or
 2. 13. An ink set comprisinga first aqueous ink and a second aqueous ink having a same color tone,wherein the first aqueous ink and the second aqueous ink contain atleast one common dye as a coloring material, the second aqueous ink hasa lower coloring material content than the coloring material content ofthe first aqueous ink, and a degree of fading of an image produced withthe second aqueous ink is the same as or lower than a degree of fadingof an image produced with the first aqueous ink.
 14. An ink setaccording to claim 13, wherein each degree of the fading of the imageproduced with the first aqueous ink and the second aqueous ink is equalto or greater than 80% residual rate of reflection density of the image.15. An ink set according to claim 14, wherein the residual rate ofreflection density of the image is obtained by irradiation with a xenonlamp at 6,000 klux·hr.
 16. An ink set according to claim 13, wherein thecolor tone is magenta.
 17. An ink set according to claim 16, wherein thesecond aqueous ink contains a dye represented by formula (I) as a solecoloring material:

wherein R1 is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof and n is 1 or
 2. 18. An ink set comprisinga first aqueous ink and a second aqueous ink having a same color tone,wherein the first aqueous ink and the second aqueous ink contain atleast one common dye as a coloring material, the second aqueous ink hasa lower coloring material content than the coloring material content ofthe first aqueous ink, and an image produced with the second aqueous inkwhen it is left under a condition that promotes fading has a residualrate of reflection density that is equal to or greater than that of animage produced with the first aqueous ink.
 19. An ink set according toclaim 18, wherein each degree of the fading of the image produced withthe first aqueous ink and the second aqueous ink is equal to or greaterthan 80% residual rate of reflection density of the image.
 20. An inkset according to claim 19, wherein the residual rate of reflectiondensity of the image is obtained by irradiation with a xenon lamp at6,000 klux·hr.
 21. An ink set according to claim 18, wherein the colortone is magenta.
 22. An ink set according to claim 21, wherein thesecond aqueous ink contains a dye represented by formula (I) as a solecoloring material:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or
 2. 23. An ink jet recordingapparatus comprising: ink storage portions storing a first aqueous inkand a second aqueous ink having a same color tone respectively, whereinthe first aqueous ink and the second aqueous ink contain at least onecommon dye as a coloring material, the second aqueous ink has a lowercoloring material content than the coloring material content of thefirst aqueous ink, and a degree of fading of an image produced with thesecond aqueous ink is the same as or lower than a degree of fading of animage produced with the first aqueous ink; and a head portion forejecting the inks.
 24. An ink jet recording apparatus according to claim23, wherein each degree of the fading of the image produced with thefirst aqueous ink and the second aqueous ink is equal to or greater than80% as residual rate of reflection density of the image.
 25. An ink jetrecording apparatus according to claim 24, wherein the residual rate ofreflection density of the image is obtained by irradiation with a xenonlamp at 6,000 klux·hr.
 26. An ink jet recording apparatus according toclaim 23, wherein the color tone is magenta.
 27. An ink jet recordingapparatus according to claim 26, wherein the second aqueous ink containsa dye represented by formula (I) as a sole coloring material:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or
 2. 28. An ink jet recordingapparatus comprising: ink storage portions storing a first aqueous inkand a second aqueous ink having a same color tone respectively, whereinthe first aqueous ink and the second aqueous ink contain at least onecommon dye as a coloring material, the second aqueous ink has a lowercoloring material content than the coloring material content of thefirst aqueous ink, and an image produced with the second aqueous inkwhen it is left under a condition that promotes fading has a residualrate of reflection density that is equal to or greater than that of animage produced with the first aqueous ink; and a head portion forejecting the inks.
 29. An ink jet recording apparatus according to claim28, wherein each degree of the fading of the image produced with thefirst aqueous ink and the second aqueous ink is equal to or greater than80% residual rate of reflection density of the image.
 30. An ink jetrecording apparatus according to claim 29, wherein the residual rate ofreflection density of the image is obtained by irradiation with a xenonlamp at 6,000 klux·hr.
 31. An ink jet recording apparatus according toclaim 28, wherein the color tone is magenta.
 32. An ink jet recordingapparatus according to claim 31, wherein the second aqueous ink containsa dye represented by formula (I) as a sole coloring material:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or
 2. 33. An ink jet recordingmethod comprising the step of applying a first aqueous ink and a secondaqueous ink having a same color tone to a recording medium, wherein thefirst aqueous ink and the second aqueous ink contain at least one commondye as a coloring material, the second aqueous ink has a lower coloringmaterial content than the coloring material content of the first aqueousink, and a degree of fading of an image produced with the second aqueousink is the same as or lower than a degree of fading of an image producedwith the first aqueous ink.
 34. An ink jet recording method according toclaim 33, wherein each degree of the fading of the image produced withthe first aqueous ink and the second aqueous ink is equal to or greaterthan 80% residual rate of reflection density of the image.
 35. An inkjet recording method according to claim 34, wherein the residual rate ofreflection density of the image is obtained by irradiation with a xenonlamp at 6,000 klux·hr.
 36. An ink jet recording method according toclaim 33, wherein the color tone is magenta.
 37. An ink jet recordingmethod according to claim 36, wherein the second aqueous ink contains adye represented by formula (I) as a sole coloring material:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or
 2. 38. An ink jet recordingmethod comprising the step of applying a first aqueous ink and a secondaqueous ink having the same color tone to a recording medium, whereinthe first aqueous ink and the second aqueous ink contain at least onecommon dye as a coloring material, the second aqueous ink has a lowercoloring material content than the coloring material content of thefirst aqueous ink, and an image produced with the second aqueous inkwhen it is left under a condition that promotes fading has a residualrate of reflection density that is equal to or greater than that of animage produced with the first aqueous ink.
 39. An ink jet recordingmethod according to claim 38, wherein each degree of the fading of theimage produced with the first aqueous ink and the second aqueous ink isequal to or greater than 80% residual rate of reflection density of theimage.
 40. An ink jet recording method according to claim 39, whereinthe residual rate of reflection density of the image is obtained byirradiation with a xenon lamp at 6,000 klux·hr.
 41. An ink jet recordingmethod according to claim 38, wherein the color tone is magenta.
 42. Anink jet recording method according to claim 41, wherein the secondaqueous ink contains a dye represented by formula (I) as a sole coloringmaterial:

wherein R₁ is a substituted or unsubstituted alkoxy group or asubstituted or unsubstituted aryl group; each of R₂ and R₄ isindependently a hydrogen atom or a substituted or unsubstituted alkylgroup; R₃ is selected from the group consisting of a hydrogen atom, asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkoxy group, a substituted or unsubstituted aryloxy group, and ahalogen atom; X₁ is a carboxyl group or a salt thereof, or a sulfonicacid group or a salt thereof; and n is 1 or 2.